Lubrication of each of sliding parts of a compressor used in a refrigerator is ensured by a refrigerator oil which is compatible with a refrigerant used. When the sliding parts are made of aluminum and/or iron, however, there has still been a problem of wear and seizing. There has also been caused a problem of capillary clogging due to insufficient sludge dispersibility.
To cope with these problems, Patent Document 1 proposes the use of a refrigerator oil composition containing a base oil of a specific polyether and a phosphorothionate such as an alkyl phosphorothionate or an aryl phosphorothionate.
Patent Document 2 proposes a lubricating oil composition for a sliding part, containing a mineral oil and/or a synthetic oil and, added thereto, 0.05 to 5% by weight of a thiol.
With these proposals, however, it has still been impossible to satisfy both sludge dispersibility and performance of wear and seizure prevention of sliding parts.
In this circumstance, there is a demand to establish a refrigerator lubricating system which satisfies both sludge dispersibility and prevention of wear and seizing of sliding parts by improving the refrigerator oil or by improving both the refrigerator oil and the lubricating material.
[Patent Document 1] Japanese Unexamined Patent Publication No. 2000-17282
[Patent Document 2] Japanese Unexamined Patent Publication No. H05-117680